Boric acid INDEX

Figure 5. Effect of fire-retardant chemicals on oxygen index (21). Key V, ammonium sulfate +, sodium tetraborate decahyarate O, aisodium oc-taborate tetranydrate , boric acid A, monoammonium phosphate A, ammonium polyphosphate (11-37-0) O, zinc chloride , sodium dichromate X, untreated.

Properties Colorless liquid mild odor. Hydrolyzes rapidly depositing boric acid in finely divided crystalline form. Bp 120C, d 0.863-0.864 (20/20C), flash p 51.8F (11C) (CC), bulk d 7.20 lb/gal (20C), refr index 1.37311 (20C). 

Ethyl orthoborate has a boiling point of 120°, a density of 0.86426, and a refractive index (n ) of 1.3721. It is readily hydrolyzed to ethanol and orthoboric acid. The ester may be analyzed for boron by dissolving a weighed sample in water, adding mannitol (about ten times the weight of sample taken), and titrating the boric acid to the phenolphthalein end point. This determination works best if the solution is protected from atmospheric carbon dioxide in the region of the end point. 

Determinations of the refractive index and thickness of oxide films formed by various methods on silicon have been made by Archer and by Claussen and Flower " using ellipsometry. Archer found a refractive index of 1.362 for an oxide film formed in an aqueous solution of 0.1 M sodium borate and 0.1 M boric acid. Claussen and Flower found that the refractive index of the oxide formed in 0.0025 N KNO3 anhydrous N-methylacetamide was 1.468 and that of films formed in 0.04 iV KNO3 in N-methylace-tamide with 6-8% water was 1.417. Zobel and Young using Lewis method " with liquids of known refractive index, and ellipsometry, have observed a refractive index for films formed in the above aqueous borate solution of about 1.4. Care has to be taken to check that film breakdown effects do not render the film untypical. 

Studies of borate salts as a class are indexed at this heading. For subclasses (e.g., alkali metal borates), specific salts, and esters, see the acid headings, such as Boric acid HBO2) adhesives, chem. structure of, for repair of furnace linings, R 26221c... 

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